A digital camera collects light on an electronic image sensor during a selected time period in order to produce a digital image. Complementary Metal Oxide Semiconductor (CMOS) image sensors (such as those used in cell phone cameras) are generally formed of a grid of photosites (pixels) that convert light shining on them to electrical charges. These charges can then be measured and converted into digital numbers that indicate how much light hit each photosite. As the lens of the digital camera focuses the scene on the image sensor, some pixels record highlights, some shadows, and others record all of the levels of brightness in between. The brighter the light, the higher the electrical charge. When the selected time period has expired and the exposure is complete, the image sensor “remembers” the pattern it recorded. The various levels of charge are then converted to digital numbers that can be used to recreate the image. Systems that include CMOS image sensors generally include (1) the image sensor itself, i.e., arrays of pixels that convert light energy into analog electrical signals, (2) analog sensors and converters that extract the analog signals from the pixel array and convert them to digital signals for further processing, (3) a timing controller that generates detailed control signals for controlling the pixel array, analog sensors, and an image processor, and (4) an image processor that converts the digital signals into actual image data. The image sensor generally operates under the control of an external processor (e.g. a cell phone processor or other computer). The external processor can accept the image data and can perform appropriate operations. It can also direct the image sensor as to when to acquire an image and controls certain other operational parameters.
The technology of sensor pixels and related analog processing is rapidly evolving and is frequently sensitive to precise timing of control signals. Current systems control and process sensor pixels in a mask-determined silicon chip array, which can require a large expense and lead-time to implement modifications. Therefore, a system is needed in which the precise timing of control signals can be changed without changing a silicon chip array.
Prior approaches to changing control signal timing without silicon chip modifications usually involve one of two mechanisms:
(1) A set of start/stop registers with counter decoders for each control phase; or
(2) A Random Access Memory (RAM) with a shift register for each signal.
These approaches have at least the following limitations. The first approach requires that the total number of pulses for each timing control signal and each timing control phase be known before the design is complete. The second approach requires multiple RAMs and shift registers for each timing control phase.
What is needed is a product and method that offer a means for generating a variety of signals in such a manner that the timing can be economically changed with some precision.